Electric-furnace system



June 7 1927.

1,631,667 J. BECKMANN ELECTRIC FURNACE SYSTEM Filed March 3. 1927Inventon Johannes Beckmann His Attorney Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

J'OHANNES IBEOKMANN, OF CHARLQ'I'TENBUBG, GERMANY, ASSIGNOB 'IO GDTEBALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-FURNACE SYS'IEI.

Application filed larch 8, 1927, Serial No. 172,446, and in GermanyAugust 19, 1998.

My invention relates to electric furnace s stems, more particularly tohigh frequency elhctric furnace systems, and has for its object theprovision of a simple and reliable 6 system of this character.

It is known, both with a view to improving the power factor as well asto obtain resonance, to place condensers in A. C. networks or circuitsin parallel or in series with inductive resistances. This method is ofparticular importance when the load on the generator is mainly orexclusively an inductive one, such for example, as in high fre- 'quencyfurnaces. Such known connections or high frequency furnaces, however,present various drawbacks. Where the condenser is connected in parallel,the generator only acts upon the condenser if the inductive resistancesuddenly drops out, such as in the event of an open circuit in thefurnace coil, which entails inadmissibly highjvoltages owing toexcitation of the generator by the leading current taken by thecondenser notwithstanding any voltage regulators that may have beenprovided.

According to my invention'these overvolt ages are avoided by subdividingthe furnace coil and by connecting condensers in parallel with each partof the'coil. Should any part of the coil now be interrupted by an opencircuit, there still remains the other coil section or sections whoseinductive reactance limits the leading current in the generator armatureto values which can be handled by the voltage regulator.

The accompanying drawing is a diagrammatic representation of a system ofconnections embodying my invention.

Referring to the drawing, the furnace coil 1 surrounding the crucible 2is connected in the circuit 3, connected with any suitable source of A.C. 4. In the form shown, the coil 1 is subdivided into two approximatelyor exactly equal parts 5 and 6; Condensers 7 and 8 are connected inparallel with the sections 5 and 6 of the 0011 respectively, a conductor9 connecting the point of division 10 between the coil sections with apoint 11 between the condensers. .If desired an connected in wattlesscurrent. If the condensers are.cor-

rectly proportioned, an approximate resonance of the oscillating circuitmay be brought about. An interruption of a coil 7 or 8 entails no excessvoltage, owing to the inductive reactance of the other coil 8 or 7remaining effective. In such case the generator may also be disconnectedby means of overload cutouts, because the current in thenon-disconnected half coil rises.

It will be-understood that the furnace coil may be divided into morethan two sections, if desired, and that these sections may or ma not beequal.

at I claim as new and desire to secure by Letters Patent of theUnitedStates is:

1. The combination with a high frequency electric furnace, of a highfrequency 0011 therefor divided into sect1ons, and condensers connectedacross said sections.

2. The combination with a high frequenc electric furnace, of a. highfrequency coil therefor, an intermediate connection dividing said coilinto sections, anda condenser parallel with eachof said sections. 4

3. The combination with an electric furnace provided with a highfrequency coil, of an electrical connection leading to an intermediateoint of said coil, and condensers connecte across the portions of saidcoil on opposite sides of said intermediate point.

4, The combination with an electric furnace provided with a highfrequency heating coil, of an earth connection leading to anintermediate point of said coil, and a con de iser connected across eachportion of said co1 ln witness whereof, I have hereunto set my hand this14th day of Febi-uary 192.7.

JOHANNES BECKMANN.

